It consists of two parts: the first solidly connected with the temporal bone, close to the tympanic cavity; the second soft, partly ligamentous, partly cartilaginous, directed towards the nasopharynx.
Since its first description by Eustachius, the concept of the Eustachian tube as partly bony structure has taken deep roots in our understanding of its anatomy, function, and possible dysfunction. Microscopic and gross anatomical observations of the “bony tube” have made a distinction between “the protympanum,” a tympanic cavity structure, and a more anterior and inaccessible “bony Eustachian tube.” Endoscopic observation of that area allows a very different view of anatomy and renders this distinction arbitrary and irrelevant.
While the protympanum was once a difficult-to-access region of the middle ear, the adoption of middle-ear endoscopes and angled instrumentation has made direct viewing and access feasible. Indeed, by observing the protympanum from this perspective, it is clear that the bony Eustachian tube and the protympanum are essentially one and the same.
The Eustachian tube as viewed endoscopically does not have a bony portion. It is a fibrous/cartilaginous structure that stretches from the nasopharynx to the most anterior part of the tympanic cavity (the protympanum). Its two openings are strikingly similar cufflike protrusions into the relevant space. This new understanding allows a more clear and distinct anatomical description of an area that is increasingly accessible for surgical interventions.